1. Field of the Invention
The present invention relates to a dome switch device. More particularly, the present invention relates to a dome switch device which enables electric contact by pressing.
2. Description of the Related Art
Generally, the term “portable communication devices” refers to devices by which wireless communication can be performed, while the devices are being carried. The above-mentioned portable terminals always include an antenna apparatus, a data input/output device, and a data transceiver. For the data input device, a keypad with a plurality of key buttons, which allows data input through a finger press task, is generally used. For the data output device, a display device is generally used.
The keypad typically includes dome switches for switching on/off an electric signal by being pressed by the key buttons.
As shown in FIGS. 1 through 3, a conventional dome switch 1 includes external contact portions 2a (FIG. 3) having the positive polarity “+” provided on a substrate 2 and internal contact portions 3 having the negative polarity “−”, which recognize an electric signal by contacting the external contact portions 2a. The internal contact portions 3 are formed of dome sheets designed to be elastically deformed, typically by finger pressure.
In this state, as shown in FIGS. 2 and 3, upon the user's pressing of the dome sheet 3, a central portion of the dome sheet 3 moves downward and thus physically and electrically contacts the external contact portion 2a provided on the substrate 2, thereby generating a key input signal.
Recently, with the increasing popularity of “smart” phones, a portable communication device having a keypad with a QWERTY arrangement is often used and thus the number of dome switches 1 also increases as shown in FIG. 1.
As shown in FIG. 2, a plurality of dome switches 1 are independently arranged under a key button 4 longitudinally extending in the keypad having the QWERTY arrangement.
The extending key button 4 may comprise a space bar or an enter key and has at least one boss that extends over the dome 3 to transfer the finger pressure from above on the button 4.
As shown in FIGS. 2 and 3, however, when a region other than a central region of the dome switches 1 arranged under the boss(es) extending from key button 4 is pressed, the dome sheet 3 and the external contact portion 2a of the substrate 2 do not electrically contact, thus failing to recognize a key input signal or degrading a clicking sense. Moreover, since the central region of the dome switches 1 has to be consecutively pressed for correct key input, a central region of the key button 4 corresponding to the central region of the dome switches 1 can become worn out or the tension of the dome sheet 3 can become degraded over a relatively short period of time.
As shown in FIG. 2, the plurality of dome switches 1 have to be arranged under the boss(Es) extending from key button 4, increasing a manufacturing cost and assembly processes of a product.
Therefore, in the former case, there is a need in the art to improve the accuracy of key input and the clicking sense of the dome switches or to prevent abrasion of the key button and degradation of the tension of the dome sheet, a device for recognizing a signal based on electric contact upon pressing of a central region or any other region of the dome sheet.
In the latter case, there is a need in the art to eliminate the requirement of installing several dome switches under the bosses extending from the key button, and for a device in which a dome switch also extends along the substantial areas of the key button.